It may just be the circles I travel in, but I'm hearing of a whole ton of new unnatural link notices going out in GWT today.
One of my websites received an unnatural link notice today. In my situation, I had example.net as my domain and had a website on it for years. I then got example.com and 301'd example.net over there. In March, www.example.com received an unnatural link warning and was penalized (it deserved to be). I've spent the last four month cleaning up the backlinks for both example.com and .net and have been in touch with Google about getting unpenalized (they partially lifted the penalty but I haven't seen any movement at all in the SERPs). Today, both example.net and www.example.net received unnatural link warnings 1 minute apart. That's not a typo - it's the same domain, two different hostnames. Previously, only www.example.com received the warning. I have not done any link building to example.net (and in fact, I've done nothing but remove links to this domain) over the past four month. There isn't even a website on this domain - it just 301's to example.com. I emailed Google asking why it received a warning and I'm waiting for a response. I have a feeling I've pissed off someone with my attempts to get links removed and they have launched a negative SEO attack against me (no proof yet other than the warning I just received). I'm not really sure what to do at this point though. I can't control who links to me and I'm sure I've made enemies in getting links removed so I wouldn't be surprised if I'm getting hit with a ton of links right now.